GAPP Induction and Concurrent Chemoradiotherapy for High-risk Locoregionally Advanced NPC.

Inclusion Criteria: * Voluntary participation and signed informed consent. * Age 18-65 years, male or non-pregnant female. * Pathologically confirmed non-keratinizing nasopharyngeal carcinoma (differentiated or undifferentiated type, i.e., WHO type II or III). * Previously untreated patients with no history of other malignancies; initial treatment for nasopharyngeal carcinoma. * Stage III: TanyN3M0 / T4N0-2M0 (9th AJCC/UICC staging system). * ECOG performance status 0-1, with no severe dysfunction of vital organs (heart, lung, liver, kidney, etc.). * Hemoglobin (HGB) ≥90 g/L, white blood cell count (WBC) ≥4.0×10\^9 /L, platelet count (PLT) ≥100×10\^9/L. * Liver function: ALT and AST \<2.5× upper limit of normal (ULN); total bilirubin \<2.0×ULN. * Renal function: serum creatinine \<1.5×ULN. Exclusion Criteria: * Patients with recurrent or distant metastatic nasopharyngeal carcinoma. * Pathologically confirmed keratinizing squamous cell carcinoma (WHO type I). * Receipt of systemic or topical glucocorticoid therapy within 4 weeks prior to enrollment. * Participation in another clinical trial of an investigational drug within 3 months prior to treatment. * Known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation. * Patients with idiopathic pulmonary fibrosis, drug-induced pneumonitis, organizing pneumonia (i.e., bronchiolitis obliterans), radiation pneumonitis that is clinically symptomatic or requires steroid therapy, active pne…